Converting Ext4 to JFS

Because I have an older laptop and disk I/O can really bottleneck on the motherboard, I decided to move from the ext4 filesystem to JFS. Recently, I’ve used ext4 because it was fairly fast and definitely reliable; however, with the kernel moving to 2.6.30 new data integrity features have been added that slow it fairly noticeable on an eight year old computer. Moving to JFS has made a fair difference in improving the speed of the system, it’s caveat being that it that journals only metadata (not metadata and data like ext3/4)).

Backup, Convert, Restore

The JFS filesystem utilities will be needed (for Debian/Ubuntu):

sudo apt-get install jfsutils

Reboot to a rescue CD, and backup partition(s)/disks onto another drive. For this example two partitions are used: one for root, one for home. Mount root, home, and then the backup drive:

The fstab file (the static filesystem configuration) needs to be updated. The information that will need adjusting is: the UUID (possibly), the filesystem type, and options. The UUID’s (unique disk identifiers) may have changed, they can be appended onto the fstab file (so that they can be easily moved) like this:

noatime lessens disk writes by not creating a timestamp every time a file is accessed (it isn’t seen as very useful anymore since it was developed primarily for servers with statistics in mind).

JFS supposedly works very well with the Deadline Scheduler; the Grub configuration need to specify to use it. This example is for Grub2 though it is similar with original Grub; edit /etc/default/grub and append:

...
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash elevator=deadline"
...

The other Grub configurations need to be updated with the new information:

update-grub

Then the Grub bootloader will have to be re-installed to the MBR (I think this is because the version of Grub put on the MBR has directions on how to be able to find its configurations for a specific filesystem).

Not ready to try btrfs yet but your ext4 creation is interesting. These all appear to be good options, will have to try. A little interested in why you choose -m as zero though. From the man page I’m reading it says:

-m reserved-blocks-percentage
Specify the percentage of the filesystem blocks reserved for the
super-user. This avoids fragmentation, and allows root-owned
daemons, such as syslogd(8), to continue to function correctly
after non-privileged processes are prevented from writing to the
filesystem. The default percentage is 5%.

Seems like this would be a good thing, particularly for the fragmentation bit.

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